OFFSET
0,7
FORMULA
G.f.: (1+x)^2/(1+x^2)/(1+2*x+2*x^2)/(1-x).
PROG
(PARI) {a(n)=polcoeff((1+x)^2/(1+x^2)/(1+2*x+2*x^2)/(1-x+x*O(x^n)), n)}
CROSSREFS
KEYWORD
sign
AUTHOR
Paul D. Hanna, Apr 27 2006
STATUS
approved